1. Field of the Invention
The present invention is generally related to a manually controlled throttle system and, more particularly, to a calibration strategy that minimizes potential errors that could otherwise result from the buildup of manufacturing and assembly tolerances within the throttle control system.
2. Description of the Prior Art
Manually controlled throttle systems, used in conjunction with marine vessels, are well known to those skilled in the art. In many different types of pleasure craft, the operator of the marine vessel is provided with a manually movable hand lever or levers which can be used by the operator to select both engine speed and gear choice. With regard to engine speed, the operator is typically provided with a choice from idle speed to wide open throttle (WOT). With regard to gear selection, the operator is typically provided with choices of forward, neutral, or reverse gear positions. In drive-by-wire systems, the position of the manually operated handle, or lever, is sensed by an appropriate sensor, such as a potentiometer, and a signal is provided to a microprocessor. That signal is representative of the position of the manually movable throttle handle. The microprocessor then interprets the desired engine speed from the received signal and controls the actual throttle and/or fuel injectors of the engine to obtain the desired speed as requested by the operator of the marine vessel.
U.S. Pat. No. 6,414,607, which issued to Gonring et al on Jul. 2, 2002, discloses a throttle position sensor with improved redundancy and high resolution. A throttle position sensor is provided with a plurality of sensing elements which allow the throttle position sensor to provide a high resolution output to measure the physical position of a manually movable member, such as a throttle handle, more accurately than would otherwise be possible. The plurality of sensors significantly increases the redundancy of the sensor and allows its operation even if one of the sensing elements is disabled.
U.S. Pat. No. 6,273,771, which issued to Buckley et al on Aug. 14, 2001, discloses a control system for a marine vessel. The control system incorporates a marine propulsion system that can be attached to a marine vessel and connected in signal communication with a serial communication bus and a controller. A plurality of input devices and output devices are also connected in signal communication with the bus and a bus access manager, such as a CAN Kingdom network, is connected in signal communication with the controller to regulate the incorporation of additional devices to the plurality of devices in signal communication with the bus, whereby the controller is connected in signal communication with each of the plurality of devices on the communication bus. The input and output devices can each transmit messages to the serial communication bus for receipt by other devices.
U.S. Pat. No. 5,664,542, which issued to Kanazawa et al on Sep. 9, 1997, describes an electronic throttle system. On one side of a valve shaft, there are provided an accelerator drum connected to an accelerator pedal by an accelerator wire, a return spring for urging the accelerator drum in a valve closing direction, and an accelerator sensor for detecting rotation of the accelerator drum and transmitting a detected signal to a host system. On the other side of the valve shaft, there are provided a large-diameter gear and an opening sensor. An armature of a solenoid clutch is attached to the gear and held on a motor shaft via a slide bearing. Thus, the motor, the solenoid clutch, and the throttle valve are arranged in a U-shape form for interconnection through four gears.
U.S. Pat. No. 6,095,488, which issued to Semeyn, Jr. et al on Aug. 1, 2000, describes an electronic throttle control with adjustable default mechanism. The system has a housing with a motor, throttle valve, gear mechanism, and fail-safe mechanism. A spring member attached to a gear member and default lever, and which is biased when the throttle valve is in its fully open and closed positions, operates to open the throttle valve in the event of an electric failure, thus allowing the vehicle to limp home. An adjustable pin member is used to adjust the position of the default lever and thus the throttle valve in a fail-safe situation.
U.S. Pat. No. 5,381,769, which issued to Nishigaki et al on Jan. 17, 1995, describes a throttle valve drive apparatus. It comprises an actuator which serves to mechanically drive a throttle valve disposed in an intake passage of an internal combustion engine and is controlled in accordance with an instruction from a control unit, an accelerator lever which serves to mechanically drive the throttle valve and to adjust the opening degree of the throttle valve in accordance with an amount of operation performed by an operator. A first clutch disposed between rotary shafts of the actuator and the throttle valve and serving to transmit a turning force from the actuator to the throttle valve, and a second clutch disposed between rotary shafts of the accelerator lever and the throttle valve and serving to transmit the turning force from the accelerator lever to the throttle valve. An engaging force of the first clutch is discriminated from that of the second clutch, one of the first and second clutches having a greater engaging force comprising an on-off constant engagement type clutch, the other clutch having a smaller engaging force comprising a constant engagement type clutch, and the on-off type clutch is switched on and off so as to transmit the turning force to the throttle valve selectively from the actuator or the accelerator lever.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
Unlike known throttle control systems for marine vessels, in which push-pull cables connect a manually movable lever to the actual throttle control linkage system of the marine propulsion device, drive-by-wire throttle control systems provide electrical signals between a manually controllable throttle lever mechanism and an engine control unit of the marine propulsion device. A sensor is provided to detect the physical position of the manually movable handle and the sensor provides electrical signals, on the signal wires, to the engine control unit (ECU) associated with the one or more engines of a marine propulsion system. This type of system requires that the sensor be sufficiently accurate to measure and provide appropriate signals representing the physical position of the manual movable handle. Because of the potential buildup of tolerances during the manufacture of the manually controllable lever and associated equipment, the signal provided by the position sensor may not be completely reliable with regard to the precise position of the handle.
It would therefore be significantly beneficial if a system could be provided that accurately and efficiently allows the calibration of a drive-by-wire throttle control system.
A method for operating a throttle control system, in accordance with the preferred embodiment of the present invention, comprises the steps of providing a manually operated throttle controller, providing a sensor connected to the manually operated throttle controller and having an output which is representative of the position of the manually operated throttle controller, and providing a microprocessor connected in signal communication with the sensor and having an input connected in signal communication with the output. The present invention further comprises the steps of receiving a first position indicating signal from the sensor which is representative of a first known position of the manually operated throttle controller and receiving a second position indicating signal from the sensor which is representative of a second known position of the manually operated throttle controller.
In its most basic application, the present invention reads the first and second position indicating signals and stores those indicating signals for later use during the operation of a marine vessel. After the calibration is complete, the method for operating the throttle control system of the present invention further comprises the steps of receiving a subsequent position indicating signal from the sensor which is representative of a subsequent position of the manually operated throttle controller and then calculating the subsequent position of the manually operated throttle controller as a function of the subsequent position indicating signal and the first and second position indicating signals.
As will be described in greater detail below, each of the position indicating signals received by the microprocessor actually comprise three distinct magnitudes of three signals. The three signals are intended to be generally redundant to each other and are provided for purposes of accuracy and redundancy in the event that one or more of the three signals are unavailable to the system.
In a particularly preferred embodiment of the present invention, the method comprises the steps of receiving first, second, third, fourth, and fifth position indicating signals from the sensor which are representative, respectively, of first, second, third, fourth, and fifth known positions of the manually operated throttle controller, or lever handle. The receipt and storage of five position indicating signals allows the present invention to determine whether the throttle handle is in a neutral position range, whether the throttle handle is in a forward gear selection position or reverse gear selection position, and also allows the present invention to determine the percentage of wide open throttle engine speed that is being currently requested by the operator of the marine vessel. In the particularly preferred embodiment of the present invention, the first and fifth known positions correspond to reverse and forward maximum throttle positions. The second and fourth known positions correspond to the reverse and forward shift detent positions that signify the transition location between the neutral gear position and both reverse and forward gear positions. The fifth known position is a detent location that is generally in the center portion of the neutral gear selection range.